1. Field of the Invention
The present invention relates to an image reading device, an image reading method, an image forming apparatus, and a computer-readable recording medium.
2. Description of the Related Art
Some image reading devices are those provided with a function of determining the size of a document when a pressure plate provided in its upper portion is closed. Particularly, in a device whose image reading speed is fast, a light source needs to irradiate the document with a large amount of light, which may cause a user to feel glare when he/she determines the size of the document. In order to reduce the glare perceived by the user, a technology is known in which the light amount irradiated by the light source is reduced at the time of determining the size of the document.
Japanese Patent No. 5087590 discloses an image reading device that adjusts, when an image reading unit is in a standby mode, an operation clock so that a mask period as a stop period of the operation clock to an image sensor is prolonged longer than that in a normal operation mode of the image reading unit as compared with the operation clock in the normal operation mode of the image reading unit while maintaining the frequency of the operation clock to a reading control unit and the image sensor.
However, conventionally, there is a problem that reading a document at a high speed and reducing glare perceived by the user when determining a document size are not compatible.
In view of the conventional problem, there is a need to provide an image reading device, an image reading method, an image forming apparatus, and a computer-readable recording medium having a computer program capable of achieving a balance between reading a document at a high speed and reducing glare perceived by the user when determining a document size while preventing erroneous determination of the document size.